Tablet coating machine



March 31, 1959 W. K. WYATT, JR., ETAL TABLET COATING MACHINE Filed July 2o,' 1954 v 5 Sheets-Sheet 1 March 31, 195% w. K. WYATT, JR., ET AL 2,879,724

' TABLET COATING MACHINE 5 Sheets-Sheet 2 Filed July 20, 1954 March 31, 1959 w. K. WYATT, JR, ET AL 2,879,724

TABLET COATING MACHINE Filed July 20, 1954 s Sheets-Sheet 3 w-. K. WYATT, JR., ET AL 2,879,724 I March 31, 1959 TABLET COATING MACHINE Filed July 20, 1954 5 Sheets-Sheet 4 March 31, 1959 w. K. WYATT, JR., ET AL 7 4 TABLET COATING MACHINE 5 Sheets-Sheet 5 Filed July 20, 1954 United States Patent 2,879,724 TABLET course ACHINE William Kirk Wyatt, Jr., Souderton, and John R. Brownell, Telford, Pa., assignors, by mesne assignments, to F. J. Stokes Corporation, Philadelphia, Pa., a company of Pennsylvania Application July 20, 1954, Serial No. 444,564 9 Claims. cii' ring-1 This invention relates to pill or tablet coating machines convenience, we shall refer to the previously compressed tablet as the core tablet, and the exterior covering of granular material, whether it be a coating to protect or disguise the inner or core tablet or an exterior covering of medicinal material, as a coating.

The invention is particularly concerned with tabletforming machines having rotary die blocks with upper and lower punches operating in an annular arrangement of circumferentially spaced dies, a typical machine of this type being known as the Stokes BB2.

In copending applications Serial Nos. 224,608 and 277,436, filed May 4, 1951 and March 19, 1952, respectively, now US. Patents 2,700,938 and 2,727,473, certain improvements in tablet-forming machines are described and claimed for depositing a core tablet in each die over a previously deposited body of granular coating material.

The apparatus of the above mentioned Patent No.

2,727,473 comprises improvements in rotary tablet-form and top punches operating in the dies, with cam means for the movement of the punches, means for feeding granular material into the dies, and means for driving the punches to final compression. The improved apparatus of that application comprises separate feeding means, one to apply a lower layer of granular material in each die, means for precisely depositing a core tablet on the bottom layer of material in each die, and the other feeding means to apply a top layer of the material over a deposited core tablet. The apparatus also comprises cam means for operating the bottom punches which are constructed and arranged to effect a sequence of movements of the punches with respect to the movement of the rotary dies,

the coating material feeding means, and the means for depositing the core tablets in the centers to form a coating of uniform thickness over each core tablet. The apparatus includes a rotary core tablet feeder, advantageously a feeder having individual receptacles or pockets for the core tablets arranged to travel in synchronism with the dies, the centers of the core tablets being moved in the same direction and with the same peripheral speed as the centers of the dies, and means for depositing each core tablet on the material in the precise center of each die during continuous movement of both. The cam means are advantageously so constructed and arranged that they hold the bottom punches at a position with the upper surface of the material at almost the level of the die at the instant of deposition, and after deposition quickly lower the punches "to draw the core tablet which 2,879,724 Patented Mar. 31,,1959

and provides in combination therewith improved means for driving the rotary core tablet feeder, and for adjusting its position with respect to the dies.

It has been found that the dies in tablet-forming machines presently available are not spaced apart in the die bed with sufficient uniformity to achieve uniform centering of the core tablets with the apparatus of said patent applications. Moreover, at the high speeds necessary for commercial operations even slight variations interfere with uniform coating of the core tablets, and the invention provides such precise. and positive control of the adjustments as to make high speed coating operations commercially feasible, for example, the improved machine of the invention coats over 30,000 tablets per hour.

This invention provides an improvement over the core tablet centering apparatus of said applications which automatically adjusts the precise point of core-tablet deposition in each die, and comprises means for making small but precise adjustment in the point of deposition for each die to compensate for the variations in spacing from die to die.

The rotary core tablet feeder is a flat disc with peripheral pockets for carrying the tablets over a stationary plate located over the dies and by means of which the tablets are held out of contact with the die bed until pushed over the end of the plate and into the dies. The invention provides a core tablet feeder assembly securely connected to the tablet machine comprising a toothed drive wheel member in gear-like connection with the die punches which drives through a shaft the core tablet feeder disc. The toothed wheel has bearing teeth corresponding in number and spaced alignment with the pockets of the feeder disc whereby the bearing surface of the teeth bear a precise operatively aligned position with the tablet-contacting edges of the pockets. I'he feeder assembly comprises means for adjustably securing the position of the feeder disc in a precise position relative to the bearing surfaces of the toothed drive wheel and the centers of the dies. The toothed wheel has a spring pressed oscillatory member with fingers which hold each bearing tooth in'snug bearing contact with each punch and in this manner the rigidly connected feeder disc is subjected to very slight oscillations while rotatingv to locate the pockets of the feeder disc in precise position with respect to the die of the particular punch then engaged by a bearing tooth of the toothed wheel, regardless of variations in the spaces between the dies and punches.

The feeder assembly also comprises adjusting mean: for shifting and securing in position the feeder disc'with respect to the toothed wheel to move the pockets 'of the feeder disc in either the radial direction of the dies or in an advanced or retarded rotary direction and to secure the feeder disc in the desired position so thatthe tablets will be deposited in the exact center of the dies.

These and other objects of the invention will be better understood after considering the following discussion taken in conjunction with the accompanyingdrawings, in which:

Figure 1 is a plan view of the improved apparatus of" Fig. 6 is a sectional view at 6-6 of Fig. 3;

Fig 7 is a vertical rectilinear development of the rotary bed, stationary "head, plungers, and cams through the centers of the dies of Fig. 1; i

Figs. 8 to 13 are enlarged fragmentary views, partly in section, at 8 8, 9 9 10 -1l), 1111, 1 2 12 and 43- 3 lF g 7 s Fig. 1-11 isan enlarged fragmentary plan view of the parts shown in Fig. l, and i Fig. l5 is an eleyation of Fig. 14 at 15 1S.

apparatus illustrated in the drawings comprises a rotary lower block 1 having bottom punches B, a rotary upper die block 2 havingtop punches T, coating feed frames 3 and 4for introducing granular coating'mate rial into the dies from the supply hoppers or feeders 5 and and ram 9 hich car ie t e sor le f e ass y 9- Tzlir s r abl e r s em l 9 c m i s a Shaft 15, a toothed drive wheel member 16 and a core tablet feeder disc 17. The feeder assembly is so mounted that lire rotary core tablet feeder or feeder disc 17 lies over the rotary die bed 29 of the die block 2 and directly over the stationary shelf 18 which is in planar registry with the top surface of the die bed, Shelf 18 is mounted on the base 25 of the machine by posts 7. 4

The tablet feedhopper (not shown) is an apparatus forming no part of this invention and has a chute 20 which supplies core tablets and deposits them in the pockets 38 of the feeder disc.

This tablet machine comprises a stationary base on which is securely mounted the annular cam means 26 concentric with the rotary die blocks 1 and 2 and the die bed 29. The rotary part of the press comprises a lower driven block 1 which is fixedly connected to the npper die block 2 and both members rotate in unisonon shaft 27. The upper die block has an annular groove or recess 28 and a flat and horizontally disposed filling surface or die bed 29. The die bed 29 has twenty-seven tablet forming dies D annularly arranged and with their arses coincident with top punches T and bottom punches B. Any suitable number of dies and punches may be used. The bottom punches B operate in bearing bores in the punch block 1 and have integral headed lower ends in operation connection with cam means 26. The top punches T are operatively mounted in bearing bores in the upper punch block 2, each punch of which has a flared head which engages the upper stationary cam means 32. The base 25,cam means 26 and cam means 32 are stationary. The tablet machine is provided with an adjustable lower compression roller 33 and an upper fixed compression roller 34 (Fig. 7), these rollers cooperating .to drive the bottom and top punches respectively in the final compression of the coatings on the tablets.

i The usual rotary tablet-forming machine is constructed for the production of two different groups of tablets on the same die bed, one group on each'half of the machine. in such machines the feederframe 3 feeds the granular material for tablets that are completely formed and discharged before the rotating dies reach the feeder frame 4. The feeder frame 4 feeds granular material to form another set of tablets which are completely formed and discharged before the dies reach the feeder frame 3.

In this invention the feed hopper 6 and feed frame 4 are used to place in the dies what shall be referred to as the bottom fill while the identical and diametrically disposed feed hopper 5 and feed frame 3 are used to add to the dies an additional quantity of the same material w i sh rsts rr ts s t e "tenfil Thes e frames are leveling devices comprising scraper blades 35 and 36 in close contact with the die b ed'29 for scraping excess material which would otherwise project above the plat top surfaces of the dies.

2 This invention employs a tablet feed mechanism 21 ss ae ns f der sl ts 7 a Per he al p t qn o wh h is upetpsssa over the thin flat plate 37 which lies over the dis e! stasls li l t was; ssistant-. 2:; i

cured to shelf 18 and a clamping bar 23 that secures the plate 37 to the shelf 18. V This feedwheel mechanism is described and claimed in the aforementioned Patent No. 2,727,473.

The peripheral portion of the feed wheel 17 has a multiplicity of spaced pockets 38 (Figs. 3, 4 and 6) which are shaped to effect a close fit with the previously formed annular core tablets C fed into the pockets one at a time through the feed means 20. The feed wheel 17 is so proportioned and spaced with respect to the dies that the centers of the tablets in the pockets at the time of deposition coincide closely with the centers of the dies and both travel in the same direction and at the same speed when their respectively centers coincide. The points of coincidence embrace a vertical line through the centers of the pockets and dies and this is what is referred to as the transfer point. The thin arcuate metal plate 37 supports the tablets out of contact with the rotating die bed 29 asshown in Figs. 3 and 4. This plate is adjustably connected to the shelf 18 by the bar 23 (Fig. 1) so that the l ll'eme edge 4!) thereof can be located exactly in the proper place with respect to the location of the die andtlne tablet in a pocket at the time the tablet is deposition on the frame 9 by bolts 51 and 52. This base has a central bore 53 and an annular groove 54, both being concentric. An eccentric shifting device is adjustably secured to the base, comprising a flat plate 55 h vin an nnula p t cn' fi t fits l sel inside t e bore 53 and a llange 57 that fits closely in bearing condi=the r ov h Pl e is o d to w l e the stud bolts 58 and 5 9 that pass through a shift plate 60 and into a bearing shafr't 62. These three members, namely,vplates 55 and 60, and shaft 62 are securely held together .by bolts 58 and 59.

The center line L through the plate 50 and shaft 62 is eccentric with respect to the annular surfaces 54 and 57. An adjustment bolt 64 is threaded into plate 50 and passes through a slot 65 in plate 60. When bolt 64 is screwed out to remove it from locking contact with plate 60 one may turn the handle 66 which is fastened to plate 60 and shift the entire eccentric shifting device within the distance limited by the slot 65. As illustrated diagrammatically in Fig. 5,'this moves the axis L towards or --away from the dies and plungers the small distance between the broken lines as required.

The shaft 15 is rotatably mounted on the shaft 62 by bearings 67 and 68. Shaft 15 has the toothed drivc wheel 16 secured thereto by screws 70 which pass th eush and erum t r o pes ns r n heel 1. ha .b ss teet rr sp ndine in mb to the numbe .o when 8 0n t e d i 17 whi h is mo n e in a fixe ti .0 ha 15 by b lt 7. and t e dam in p at 7 E h m t of the w e a a e n block .5 f h rd st e it a nec 6 in e te n a e in the tooth n ure b h screw bss esks a e surfaces developed to malre proper mechanical contact wit P 9 d gft Pun hes a d he b ma po i i driving contact to drive shaft 15.

A floating toothed wheel 80 lies over wheel 16 and rides on the spacer ring 71. This floating plate has a plurality of holes 81 coincident with a plurality of holes 82 in wheel 16. A plurality of coil springs S are at: s e i spa-a; he pers! erss n sts at o 999 tul1 and let th ther 0 wheel 80 These p ings the tension in springs S. Thereafter the punches make contact with the developed surfaces 84 of the blocks 75 of wheel 16. By reason of the yieldable mounting of wheel '80 the teeth 83 hold surfaces 84 in direct bearing contact with each plunger. As a consequence of this wheel and tooth construction, the teeth of the drive wheel 16 bear against the punches without slack or play notwithstanding variations in the distances between the punches. The pockets 38 of the feeder disc 17, bear an aligned relation to the bearing surfaces of the blocks 75 to the end that the rotation of the dies and pockets are precisely correlated and at the point of tablet deposition are in coincidence.

"The invention also provides a means for precisely adjusting the centers of the pockets 38 circumferentially with respect to the blocks 75 and consequently, the dies. The bracket 90 (Figs. 3 and 6) attached to shaft carries an eccentric shaft 91 having an operating handle 92 connected thereto with pin 91'. The shaft part 93 turns in a hole in the bracket while the eccentric part 94 turns in the closely fitted slot '95 in wheel 17 (Figs. '3 and '6). By loosening screws 73 so that member 74 can turn in bearing 15, and turning handle 92 the .feeder disc 17 can be advanced or retarded with respect to wheel 16 as shown by the arrows Fig. 6.

Fig. 7 is a rectilinear development of the cam means, die blocks, dies, and punches of the tablet-forming machine. cam insets 96, 97, and 98 to control the positions of the bottom punches B in the dies prior to deposition of the core tablet, to vary the thickness of the coating material, and to regulate the thickness of the top fill as will be described hereinafter, fixed abrupt cam 99, and cam rails 102, 103, 104 and 105. It will be noted that all of the top punches are held by their heads on the cam 32 in an upward out-ofthe-way position until they reach the cam rail 106 which starts them in the downward direction so that they are brought under the compression roller 34 for final compression. Thereafter, they are guided upward in the cam track 107 to their upper suspended position on cam 32.

The bottom punch B on the extreme right (Fig. 7) is shown in its most elevated position supporting a coated tablet C which is removed shortly thereafter by contacting a deflecting baffle 108 (Fig. 1). .As the rotating structure comprising members 1 and 2 and their punches travel toward the left (Fig. 7), the bottom punches are moved progressively downward under the cam rail 102 as they pass under the feeder 6 and feed frame 4 to fill the spaces in the dies with the granular coating material M. At the lowermost position the dies engage the adjustable cam section 96 and are raised to remove excess material which is scraped off flush by means of scraper 36 (Fig. 1). Thereafter, the punches drop down under their own weight and engage the cam 103 to lower the upper surface of the material in the dies. Continuing from this position the punches engage the adjustable cam 97 which raises them bringing the upper surfaces of the material in the dies to the level of the surface of the die bed 29. At this point a preformed core tablet C supported on the plate 37 and in a pocket 38 of the feed wheel 17 is deposited on the upper surface of the bottom fill in the precise center of the die. At the time of deposition, the center of the die and the center of the core tablet are traveling in the same direction and at the same speed. The cam rail 104 is shaped to effect a rapid withdrawal of the bottom punch to bring the deposited tablet out of contact with the wheel 17 and also to provide space in the die for receiving the top fill of granular material. As the rotating structure with the dies continues to travel toward the left, it passes under the feeder 5 and feed frame 3 and the dies are loaded with the top fill. The dies then move into contact with the adjustable cam segment The cam means 26 includes three adjustable and 'are'q'uickly elevated while under the scraper 35 which removes all of the excess material. Continuing, the punches engage the cam rail which moves them downward and as "they travel in this position along the cam 26 they come into gradual contact with the lower adjustable press roller 33. At the same. time, the top punches T pass under the cam rail 1'06 and are positioned to pass under the top press roller 34 and the coating material, both top and bottom, is compressed under a predetermined pressure suficiently great to effect a strong adherent bonding of the coating material to the preformed core tablet. The bottom punches B then engage the cam surface '99 and are elevated while the top punches T engage the cam track 107 and are also do vated. This elevation of the punches removes the top punch from contact with the coated tablet C and further elevates the bottom punch to the position shown at the right which is above the flat surface of the die bed 29. As the rotating structure continues in the direction of the arrow, the" coated tablet strikes the deflecting bafiile 108 and is guided into the chute 109 (Fig. 1).

Figs. 8 to 13 are fragmentary sectional enlargements of the die area showing the positions of the punches at various important stages in the deposition of the coat ing material and the location of the core tablet in its precisely centered position with respect to the die. Fig. 8 shows the initial loading of the die with bottom fill M. Fig. 9 shows the measured quantity of bottom fill in the die, and Fig. 10 the elevation of this fill to apositio'n even with the upper surface of the bed at the time the core tablet is deposited. Fig. 11 shows the bottom punch withdrawn and the die cavity filled with a measured quantity of top fill and ready 'for final compression, illustrated at Fig. 12 which is the position of the punches when between the compression rollers 33 and 34 of Fig. 7. Fig. 13 shows the position of the bottom punch in its highest elevated position for the removal of the finished coated tablet C.

What is claimed is:

1. In a tablet coating machine of the type having a rotatable die bed with a multiplicity of annularly disposed dies, a member which moves in unison with the die bed having punches mounted to enter the dies, means for moving a succession of preformed core tablets to a position with the center of each core tablet coincident with the center of a die at the same speed and direction as the die at the time of coincidence and depositing each core tablet at its coincident die without interrupting the movement of the die or core tablet, the improvement which comprises a feeder disc having a plurality of pe ripheral pockets for moving the core tablets to the dies, a drive wheel in rigid connection with the feeder disc having teeth which engage the punches and rotate the feeder disc and maintain the pockets in precise alignment with the punches and dies, and means for adjusting the location of the feeder disc rotatably with respect to the drive wheel.

2. In a tablet coating machine of the type having a rotatable die bed with a multiplicity of annularly disposed dies, a member which moves in unison with the die bed having punches mounted to enter the dies, means for moving a succession of preformed core tablets to a position with the center of each core tablet coincident with the center of a die at the same speed and direction as the die at the time of coincidence and depositing each core tablet at its coincident die without interrupting the movement of the die or core tablet, the improvement which comprises a feeder disc having a plurality of peripheral pockets for moving the core tablets to the dies, a drive wheel in rigid connection with the feeder disc having teeth which engage the punches and rotate the feeder disc and maintain the pockets in precise alignment with the punches and dies, and means for adjusting the location of the feeder disc with relation to the centers of the dies.

3.. A tablet coating machine according to claim I which comprises resilient means for holding the teeth of the drive wheel in contact with the punches.

4. A tablet coating machine according to'claim 2 which comprises resilient means for holding the teeth of the drive wheel in contact with the punches.

5. In a tablet forming machine of the type having a rotary die bed and rotary punches for compressing granular material in the dies, a rotary tablet feeding means having core tablet pockets rotatable over and in synchronism with the dies for depositing core tablets in the dies, the improvement which comprises a toothed wheel in operative engagement with the punches acting as a drive gear, drive means connecting the toothed wheel with the tablet feeding means, and resilient means in operative connection with the toothed wheel to hold the punch-engaging surface of each tooth in bearing contact with each punch, whereby the pockets are maintained in precise operative relation to the punches.

6. In a tablet forming machine of the type having a rotary die bed and rotary punches for compressing granular material in the dies, a rotary tablet feeding means having core tablet pockets rotatable over and in synchronism with the dies, for depositing core tablets in the dies the improvement which comprises a toothed wheel in operative engagement with the punches acting as a drive gear, means connecting the toothed wheel with the tablet feeding means, a floating toothed wheel concentrically mounted near the said toothed wheel, and springs connecting the floating wheel to the toothed wheel which permits the floating wheel to oscillate a few de- 1 grees and the teeth thereof to bear against the punches and hold the teeth of the toothed wheel in positive contact with the punches.

7. A tablet-forming machine according'to claim. 6 which comprises a shaft connecting the toothed wheel with the rotary tablet feeding means, and eccentric means on the shaft for adjusting the position of the rotary tablet feeding means relative to the dies.

8. A tablet-forming machine according to claim 6 which comprises a shaft connecting the toothed wheel with the rotary tablet feeding means, and adjusting means connecting the shaft and the tablet feeding means for advancing or retarding the rotary movement of the tablet feeding means to bring the centers of the tablet pockets into coincidence with the centers of the dies at the time the tablets are deposited.

9. In a tablet coating machine, a rotatable die bed with a multiplicity of annularly disposed dies, a member which moves in unison with the die bed having punches mounted to enter the dies, feeder means for moving a succession of preformed core tablets to a position with the center of each core tablet coincident with the center of a die and depositing each core tablet at its coincident die cavity, and means for driving the feeder means off the punches comprising means for resiliently engaging the punches whereby an aligned relation of the feeder means and dies is obtained.

References Cited in the tile of this patent UNITED STATES PATENTS Whittemore July 18, 1939 

